Mercury is the top-identified contaminant in the environment and has been identified as a toxic agent by international advisory boards. It is the one metal that is least effectively retained by emission controls, partly due to its high vapour pressure. Once emitted, mercury may be deposited by wet and dry processes to environmental surfaces. In its vapour form, mercury can be carried long distances on wind currents, staying in the atmosphere for long periods of time. Mercury can change from one form to another in the environment (FIG. 1). For example, some types of bacteria and fungi can change mercury into its most toxic form, methyl mercury. Methyl mercury tends to be bio-magnified, accumulating to some degree in all fish, but especially in predatory fish such as shark, swordfish and large tuna, as well as in marine mammals. Mercury is also leached from flooded soil at new hydroelectric dam sites, or from any flooded area. This process can add to mercury levels in freshwater aquatic food chains in those areas. The health effects of mercury exposure depend on its chemical form (elemental, inorganic or organic), the route of exposure (inhalation, ingestion or skin contact), and the level of exposure. Vapour from liquid elemental mercury and methyl mercury is more easily absorbed than inorganic mercury salts and can therefore cause more harm.
Therefore knowledge of the different forms or speciation of atmospheric mercury is crucial for predicting its deposition and understanding its biogeochemical cycling. Presently the current techniques provide information on elemental analysis and the chemical composition of mercury species cannot be determined in detail. Mercury speciation measurement is one of the most important challenges. The current inability to measure multiple mercury species constitutes a major gap in the understanding of mercury cycling and precludes adequate conclusions by scientists and policymakers alike [1]. Presently, existing analytic techniques for atmospheric mercury only provide information on (a) total mercury; (b) elemental mercury, (c) particulate mercury, and (d) an operationally (but not chemically) defined group called reactive gaseous mercury (RGM). The detailed chemical characterization of RGM is essential in understanding properties such as solubility, gas-to-particle partitioning, as well as processes such as biomagnification and bio-accumulation in aquatic systems. Currently, the major mercury detection systems include a gold trap used in connection with cold-vapour fluorescence units or atomic absorption units for mercury analysis. Using these techniques, one can obtain total mercury concentrations, as well as accurate elemental mercury concentrations. However, obtaining accurate concentration of mercury-containing molecular species is currently not possible. Therefore, there is a need for a method and device that identifies and quantifies the many different species of mercury in air and aqueous systems.